The present invention relates to a process for preventing destructive oligomer or polymer formation in furfural and substituted furfural solutions. More particularly, the present invention is concerned with preventing such resinification of highly unstable 5-chloromethyl furfural by addition of an epoxy resin thereto.
A. P. Dunlop et al., Ind. Eng. Chem., 38, 705 (1946), disclosed that discoloration of furfural solutions due to auto-oxidation is avoided by the use of tertiary amines and phenolic antioxidants such as hydroquinone.
In U.S. Pat. No. 4,154,744, a process for the preparation of furan derivatives such as furfural, methyl furfural and chloromethyl furfural is disclosed. The compounds are obtained by acid decompositions of saccharides such as glucose, fructose, and saccharose, and are useful as intermediates for medicines and agricultural chemicals. The disclosed process employs a surfactant as an aid in preventing resinification of the furfural derivatives by the formation of a micelle-like state in the reaction mixture. The above U.S. Pat. No. 4,154,744 is herein incorporated by reference in its entirety.
It is known to add epoxy-containing compounds to polyvinyl chloride-containing resins to inhibit degradation of such polymers at elevated temperatures. The epoxies stabilize the polymer by reacting with HCl as it is released from the polyvinyl chloride resin preventing it from catalyzing further decomposition.
Despite the use of care in the preparation of the above furfural derivatives, the use of prior known methods of preventing the formation of unacceptable amounts of oligomer products in furfural derivatives made by the above process have proven unacceptable. In particular, where it is desired to provide highly pure compounds it is often advantageous to distill or otherwise purify the furfural product prior to use. Such procedures disadvantageously remove inhibitors such as soaps or surfactants or severely reduce the amounts present. At the same time, such procedures, especially distillation, expose the furfural derivatives to elevated temperatures that enhance the rate of resin formation. In addition, it has been found that the acidic conditions of reaction employed in preparation of the furfural compounds introduce small amounts of acid contamination into the desired product. This acid contamination, particularly hydrogen chloride contamination, is believed to contribute to the above-described resin formation problem through acid induced resinification.
It would be desirable to provide a process for preventing or reducing the formation of resinous reaction products of furfural compounds.
It would further be desirable to inhibit the formation of resinous reaction products of furfural compounds formed by acid induced resinification.
Additionally, it would be desirable to provide a process to inhibit the resinification of highly unstable 5-chloromethyl furfural.